1. Field of the Invention
This invention relates generally to storage and dispensing systems for the selective dispensing of gaseous reagents, e.g., hydride and halide gases, from a vessel or storage container in which the gas component(s) are held in sorptive relationship to a solid sorbent medium, and are desorptively released from the sorbent medium in the dispensing operation. The invention relates more specifically to gas cabinet assemblies containing one or more sorbent-based gas storage and dispensing vessels of such type, coupled to a gas dispensing manifold and/or other flow circuitry, to selectively dispense the gas from the vessel and gas cabinet to a downstream process unit, e.g., a semiconductor manufacturing facility.
2. Description of the Related Art
In the manufacture of semiconductor materials and devices, and in various other industrial processes and applications, there is a need for a reliable source of hydridic and halidic gases. Many of such gases, including for example silane, germane, ammonia, phosphine, arsine, diborane, stibine, hydrogen sulfide, hydrogen selenide, hydrogen telluride, and corresponding and other halide (chlorine, bromine, iodine, and fluorine) compounds, as a result of toxicity and safety considerations, must be carefully stored and handled in the industrial process facility.
The gaseous hydrides arsine (AsH3) and phosphine (PH3) are commonly used as sources of arsenic (As) and phosphorous (P) in ion implantation. Due to their extreme toxicity and high vapor pressure, their use, transportation and storage raise significant safety concerns for the semiconductor industry. Ion implantation systems typically use dilute mixtures of AsH3 and PH3 at pressures as high as 1500 psig. A catastrophic release of these high pressure cylinders could pose a serious injury potential and even death to fab workers.
Based on these considerations, the ion implant user must choose between solid or gas sources for arsenic and phosphorous species. Switching from As to P on an implanter with solid sources can take as long as 90 minutes. The same species change requires only 15 minutes with gas sources. However, arsine (AsH3) and phosphine (PH3), the two most commonly used source gases, are highly toxic. Their use has recently been the focus of widespread attention due to the safety aspects of handling and processing these gases. Many ion implantation systems utilize hydride gas sources supplied as dilute mixtures (10-15%), in either 0.44 L or 2.3 L cylinders at pressures of 400-1800 psig. It is the concern over the pressure-driven release of the gases from cylinders that has prompted users to investigate safer alternatives.
U.S. Pat. No. 4,744,221 issued May 17, 1988 to Karl O. Knollmueller discloses a method of storing and subsequently delivering arsine, by contacting arsine at a temperature of from about xe2x88x9230xc2x0 C. to about +30xc2x0 C. with a zeolite of pore size in the range of from about 5 to about 15 Angstroms to adsorb arsine on the zeolite, and then dispensing the arsine by heating the zeolite to an elevated temperature of up to about 175xc2x0 C. for sufficient time to release the arsine from the zeolite material.
The method disclosed in the Knollmueller patent is disadvantageous in that it requires the provision of heating means for the zeolite material, which must be constructed and arranged to heat the zeolite to sufficient temperature to desorb the previously sorbed arsine from the zeolite in the desired quantity.
The use of a heating jacket or other means exterior to the vessel holding the arsine-bearing zeolite is problematic in that the vessel typically has a significant heat capacity, and therefore introduces a significant lag time to the dispensing operation. Further, heating of arsine causes it to decompose, resulting in the formation of hydrogen gas, which introduces an explosive hazard into the process system. Additionally, such thermally-mediated decomposition of arsine effects substantial increase in gas pressure in the process system, which may be extremely disadvantageous from the standpoint of system life and operating efficiency.
The provision of interiorly disposed heating coil or other heating elements in the zeolite bed itself is problematic since it is difficult with such means to uniformly heat the zeolite bed to achieve the desired uniformity of arsine gas release.
The use of heated carrier gas streams passed through the bed of zeolite in its containment vessel may overcome the foregoing deficiencies, but the temperatures necessary to achieve the heated carrier gas desorption of arsine may be undesirably high or otherwise unsuitable for the end use of the arsine gas, so that cooling or other treatment is required to condition the dispensed gas for ultimate use.
The present invention contemplates a gas storage and dispensing system, for the storage and dispensing of reagent gases, such as hydride and halide gases, which overcomes the above-discussed disadvantages of the method disclosed in the Knollmueller patent.
The system of the invention is adapted for storage and dispensing of a wide variety of reagent gases, including hydride and halide gases, and is selectively operable at ambient temperature levels, but is able to effectively utilize the high storage (sorptive) capacity of physical adsorbents such as zeolite materials.
The present invention relates to a gas supply system. The gas supply system includes a gas cabinet defining an enclosure including therein a gas dispensing manifold and one or more adsorbent-based gas storage and dispensing vessels mounted in the enclosure and joined in gas flow communication with the gas dispensing manifold.
The enclosure may be maintained under low or negative pressure conditions for enhanced safety in the event of leakage of gas from the gas storage and dispensing vessel(s) in the enclosure. The gas supply system may be coupled to a downstream gas-consuming unit, such as a process unit in a semiconductor manufacturing facility, e.g., an ion implanter, an etch chamber, a chemical vapor deposition reactor, etc.
The adsorbent-based gas storage and dispensing system constitutes an adsorption-desorption apparatus for storage and dispensing of a gas, e.g., a gas selected from the group consisting of hydride gases, halide gases, and organometallic reagent gases, such as Group V compounds. The adsorption-desorption apparatus comprises:
a storage and dispensing vessel constructed and arranged for holding a solid-phase physical sorbent medium, and for selectively flowing gas into and out of the vessel;
a solid-phase physical sorbent medium disposed in said storage and dispensing vessel at an interior gas pressure;
a sorbate gas physically adsorbed on said solid-phase physical sorbent medium;
a dispensing assembly coupled in gas flow communication with the storage and dispensing vessel, and constructed and arranged to provide, exteriorly of said storage and dispensing vessel, a pressure below said interior pressure, to effect desorption of sorbate gas from the solid-phase physical sorbent medium, and gas flow of desorbed gas through the dispensing assembly;
wherein the solid-phase physical sorbent medium is devoid of trace components selected from the group consisting of water, metals, and oxidic transition metal species (e.g., oxides, sulfites and/or nitrates) sufficient in concentration to decompose the sorbate gas in said storage and dispensing vessel.
In such apparatus, the solid-phase physical sorbent medium contains less than 350, preferably less than 100, more preferably less than 10, and most preferably less than 1, parts-per-million by weight of trace components selected from the group consisting of water and oxidic transition metal species, based on the weight of the physical sorbent medium.
In the apparatus of the invention, the solid-phase physical sorbent medium concentration of trace components selected from the group consisting of water and oxidic transition metal species, based on the weight of the physical sorbent medium, desirably is insufficient to decompose more than 5%, and preferably more than 1% by weight of the sorbate gas after 1 year at 25xc2x0 C. and said interior pressure.
In another aspect, the present invention relates to an adsorption-desorption apparatus, for storage and dispensing of a gas, e.g., a gas selected from the group consisting of hydride gases, halide gases, and organometallic Group V compounds, said apparatus comprising:
a storage and dispensing vessel constructed and arranged for holding a solid-phase physical sorbent medium, and for selectively flowing gas into and out of said vessel;
a solid-phase physical sorbent medium disposed in said storage and dispensing vessel at an interior gas pressure;
a sorbate gas physically adsorbed on said solid-phase physical sorbent medium;
a dispensing assembly coupled in gas flow communication with the storage and dispensing vessel, and constructed and arranged to provide, exteriorly of said storage and dispensing vessel, a pressure below said interior pressure, to effect desorption of sorbate gas from the solid-phase physical sorbent medium, and gas flow of desorbed gas through the dispensing assembly;
wherein the solid-phase physical sorbent medium concentration of trace components selected from the group consisting of water, metals, and oxidic transition metal species, based on the weight of the physical sorbent medium, is insufficient to cause decomposition of the sorbate gas resulting in more than a 25%, and preferably more than a 10% rise in interior pressure after 1 week at 25xc2x0 C. in said storage and dispensing vessel.
In such apparatus, the solid-phase physical sorbent medium desirably contains less than 350, preferably less than 100, more preferably less than 10, and most preferably less than 1, part(s)-per-million by weight of trace components selected from the group consisting of water and oxidic transition metal species, based on the weight of the physical sorbent medium.
Still another aspect of the invention relates to an adsorption-desorption apparatus, for storage and dispensing of boron trifluoride, such apparatus comprising:
a storage and dispensing vessel constructed and arranged for holding a solid-phase physical sorbent medium having a sorptive affinity for boron trifluoride, and for selectively flowing boron trifluoride into and out of said vessel;
a solid-phase physical sorbent medium having a sorptive affinity for boron trifluoride, disposed in said storage and dispensing vessel at an interior gas pressure;
boron trifluoride gas, physically adsorbed on said solid-phase physical sorbent medium; and
a dispensing assembly coupled in gas flow communication with the storage and dispensing vessel, and constructed and arranged to provide, exteriorly of said storage and dispensing vessel, a pressure below said interior pressure, to effect desorption of boron trifluoride gas from the solid-phase physical sorbent medium, and gas flow of desorbed boron trifluoride gas through the dispensing assembly.
Although generally preferred to operate solely by pressure differential, in respect of the sorption and desorption of the gas to be subsequently dispensed, the system of the invention may in some instances advantageously employ a heater operatively arranged in relation to the storage and dispensing vessel for selective heating of the solid-phase physical sorbent medium, to effect thermally-enhanced desorption of the sorbate gas from the solid-phase physical sorbent medium.
A preferred solid-phase physical sorbent medium comprises a crystalline aluminosilicate composition, e.g., with a pore size in the range of from about 4 to about 13 xc3x85, although crystalline aluminosilicate compositions having larger pores, e.g., so-called mesopore compositions with a pore size in the range of from about 20 to about 40 xc3x85 are also potentially usefully employed in the broad practice of the invention. Examples of such crystalline aluminosilicate compositions include 5A molecular sieve, and preferably a binderless molecular sieve. Although molecular sieve materials such as crystalline aluminosilicates and carbon molecular sieves are preferred in many instances, the solid-phase physical sorbent medium may usefully comprise other materials such as silica, alumina, macroreticulate polymers, kieselguhr, carbon, etc. The sorbent materials may be suitably processed or treated to ensure that they are devoid of trace components which deleteriously affect the performance of the gas storage and dispensing system. For example, carbon sorbents may be subjected to washing treatment, e.g., with hydrofluoric acid, to render them sufficiently free of trace components such as metals and oxidic transition metal species. Potentially useful carbon materials include so-called bead activated carbon of highly uniform spherical particle shape, e.g., BAC-MP, BAC-LP, and BAC-G-70R, available from Kureha Corporation of America, New York, N.Y.
The apparatus of the invention may be constructed with a solid-phase physical sorbent medium being present in the storage and dispensing vessel together with a chemisorbent material having a sorptive affinity for contaminants, e.g., decomposition products, of the sorbate gas therein. Such chemisorbent material may for example have a sorptive affinity for non-inert atmospheric gases. Examples of potentially suitable chemisorbent materials include a scavenger for such contaminants, such as a scavenger selected from the group consisting of:
(A) scavengers including a support having associated therewith, but not covalently bonded thereto, a compound which in the presence of such contaminant provides an anion which is reactive to effect the removal of such contaminant, said compound being selected from one or more members of the group consisting of:
(i) carbanion source compounds whose corresponding protonated carbanion compounds have a pKa value of from about 22 to about 36; and
(ii) anion source compounds formed by reaction of said carbanion source compounds with the sorbate gas; and
(B) scavengers comprising:
(i) an inert support having a surface area in the range of from about 50 to about 1000 square meters per gram, and thermally stable up to at least about 250xc2x0 C.; and
(ii) an active scavenging species, present on the support at a concentration of from about 0.01 to about 1.0 moles per liter of support, and formed by the deposition on the support of a Group IA metal selected from sodium, potassium, rubidium, and cesium and their mixtures and alloys and pyrolysis thereof on said support.
By way of an example, such chemisorbent material may advantageously comprise a scavenger component selected from the group consisting of: trityllithium and potassium arsenide.
In respect of such chemisorbent materials for contaminants of the sorbate gas to be dispensed, any of a wide variety of scavengers or chemisorbent materials may be employed, including scavenger compositions of the types disclosed and claimed in U.S. Pat. No. 4,761,395 issued Aug. 2, 1988 to Glenn M. Tom, et al., and U.S. Pat. No. 5,385,686 issued Jan. 31, 1995 to Glenn M. Tom and James V. McManus, the disclosures of which hereby are incorporated herein by reference.
The chemisorbent material when employed may be utilized as a separate bed in gas communication with the bed of physical adsorbent, or alternatively the chemisorbent may be dispersed randomly or selectively throughout a bed of physical adsorbent material in the storage and dispensing vessel.
The invention in another aspect relates to an ion implantation system, comprising a reagent source for reagent source material and an ion implantation apparatus coupled in gas flow communication with such reagent source, and wherein the reagent source is of a type described hereinabove.
The present invention relates in still another aspect to a process for supplying a gas reagent selected from the group consisting of hydride gases, halide gases, and organometallic Group V compounds, such process comprising:
providing a storage and dispensing vessel containing a solid-phase physical sorbent medium having a physically sorptive affinity for said gas reagent;
physically sorptively loading on said solid-phase physical sorbent medium a sorbate gas selected from the group consisting of hydride gases and boron halide gases, to yield a sorbate gas-loaded physical sorbent medium; and
desorbing sorbate gas from the sorbate gas-loaded physical sorbent medium, by reduced pressure desorption, for dispensing thereof;
wherein the solid-phase physical sorbent medium is devoid of trace components selected from the group consisting of water, metals and oxidic transition metal species in a sufficient concentration to decompose the sorbate gas in said storage and dispensing vessel.
In a further particular aspect, the invention relates to an adsorption-desorption process for storage and dispensing of boron trifluoride, comprising:
providing a storage and dispensing vessel containing a solid-phase physical sorbent medium having a physically sorptive affinity for boron trifluoride;
physically sorptively loading boron trifluoride on said solid-phase physical sorbent medium, to yield a boron trifluoride-loaded physical sorbent medium; and
selectively desorbing boron trifluoride from the boron trifluoride-loaded physical sorbent medium, by reduced pressure desorption, for dispensing thereof.
Another apparatus aspect of the present invention relates to an adsorption-desorption apparatus, for storage and dispensing of a gas sorbable on a solid-phase physical sorbent medium, such apparatus comprising:
a storage and dispensing vessel constructed and arranged for holding a solid-phase physical sorbent medium, and for selectively flowing gas into and out of said vessel;
a solid-phase physical sorbent medium disposed in the storage and dispensing vessel at an interior gas pressure;
a sorbate gas physically adsorbed on the solid-phase physical sorbent medium;
a dispensing assembly coupled in gas flow communication with the storage and dispensing vessel, and constructed and arranged to provide, exteriorly of the storage and dispensing vessel, a pressure below said interior pressure, to effect desorption of sorbate gas from the solid-phase physical sorbent medium, and gas flow of desorbed gas through the dispensing assembly;
a cryopump coupled to the dispensing assembly for pressurizing the desorbed gas and discharging the resultingly pressurized gas.
In a further process aspect, the present invention relates to a process for storage and dispensing of a gas sorbable on a solid-phase physical sorbent medium, such process comprising:
providing a storage and dispensing vessel holding a solid-phase physical sorbent medium;
adsorbing such gas on the solid-phase physical sorbent medium;
establishing, exteriorly of the storage and dispensing vessel, a pressure below the interior pressure, to effect desorption of sorbate gas from the solid-phase physical sorbent medium, and flowing desorbed gas out of the storage and dispensing vessel;
cryopumping the desorbed gas from the storage and dispensing vessel to a predetermined pressure, wherein such predetermined pressure is higher than the pressure of the desorbed gas flowed out of the storage and dispensing vessel.
In all of the foregoing aspects, the gas storage and dispensing vessel of the invention may be deployed in a gas cabinet equipped with a gas dispensing manifold and associated flow circuitry therein, for dispensing of the gas desorbed from the sorbent material in the vessel and flowing the desorbed gas through the manifold flow circuitry and out of the cabinet to the gas-consumption unit. The gas storage and dispensing vessel and gas dispensing manifold may be associated with a pump, fan, blower, turbine, eductor, ejector, compressor, cryopump, or other motive flow means, to provide the pressure drop and extraction of the gas from the sorbent material in the vessel, for flow into the gas dispensing manifold.
Another aspect of the invention relates to a semiconductor manufacturing system, comprising a gas cabinet of the foregoing type, coupled to a semiconductor manufacturing process unit.
Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.